Technology: Windows turn rays of sunshine into power

Buildings could be made much more energy efficient by fitting their windows with a new type of transparent solar panel rather than glass. The panels are five to ten times as cheap as today's silicon-based solar cells but are just as efficient.

Michael Gratzel and colleagues in the Department of Chemistry at the Swiss Federal Institute of Technology in Lausanne describe their patented panel in Nature this week (24 October, p 737). The sandwich arrangement of the panel mimics the way that plants make their food by gathering energy from light through photosynthesis.

The beauty of the panels, says Gratzel, is that they are made entirely from common materials, except for the specialist conducting glass which forms the 'bread' of the sandwich. Also, the panels are easy to assemble. 'You could make one in around two hours,' he says.